[Not Applicable]
1. Field of the Invention
The present invention relates to a set of wood golf club heads that have different loft angles. More specifically, the present invention relates to a set of wood golf club heads that vary the striking plate thickness of each based on the loft angle of each wood golf club head.
2. Description of the Related Art
When a golf club head strikes a golf ball, large impacts are produced that load the club head face and the golf ball. Most of the energy is transferred from the head to the golf ball, however, some energy is lost as a result of the collision. The golf ball is typically composed of polymer cover materials (such as ionomers) surrounding a rubber-like core. These softer polymer materials having damping (loss) properties that are strain and strain rate dependent which are on the order of 10-100 times larger than the damping properties of a metallic club face. Thus, during impact most of the energy is lost as a result of the high stresses and deformations of the golf ball (0.001 to 0.20 inches), as opposed to the small deformations of the metallic club face (0.025 to 0.050 inches). A more efficient energy transfer from the club head to the golf ball could lead to greater flight distances of the golf ball.
The generally accepted approach has been to increase the stiffness of the club head face to reduce metal or club head deformations. However, this leads to greater deformations in the golf ball, and thus increases in the energy transfer problem.
Some have recognized the problem and disclosed possible solutions. An example is Campau, U.S. Pat. No. 4,398,965, for a Method Of Making Iron Golf Clubs With Flexible Impact Surface, which discloses a club having a flexible and resilient face plate with a slot to allow for the flexing of the face plate. The face plate of Campau is composed of a ferrous material, such as stainless steel, and has a thickness in the range of 0.1 inches to 0.125 inches.
Another example is Eggiman, U.S. Pat. No. 5,863,261, for a Golf Club Head With Elastically Deforming Face And Back Plates, which discloses the use of a plurality of plates that act in concert to create a spring-like effect on a golf ball during impact. A fluid is disposed between at least two of the plates to act as a viscous coupler.
Yet another example is Jepson et al, U.S. Pat. No. 3,937,474, for a golf Club With A Polyurethane Insert. Jepson discloses that the polyurethane insert has a hardness between 40 and 75 shore D.
Still another example is Inamori, U.S. Pat. No. 3,975,023, for a Golf Club Head With Ceramic Face Plate, which discloses using a face plate composed of a ceramic material having a high energy transfer coefficient, although ceramics are usually harder materials. Chen et al., U.S Pat. No. 5,743,813 for a Golf Club Head, discloses using multiple layers in the face to absorb the shock of the golf ball. One of the materials is a non-metal material.
Lu, U.S. Pat. No. 5,499,814, for a Hollow Club Head With Deflecting Insert Face Plate, discloses a reinforcing element composed of a plastic or aluminum alloy that allows for minor deflecting of the face plate which has a thickness ranging from 0.01 to 0.30 inches for a variety of materials including stainless steel, titanium, KEVLAR(copyright), and the like. Yet another Campau invention, U.S. Pat. No. 3,989,248, for a Golf Club Having Insert Capable Of Elastic Flexing, discloses a wood club composed of wood with a metal insert.
Although not intended for flexing of the face plate, Viste, U.S. Pat. No. 5,282,624 discloses a golf club head having a face plate composed of a forged stainless steel material and having a thickness of 3 mm. Anderson, U.S. Pat. No. 5,344,140, for a Golf Club Head And Method Of Forming Same, also discloses use of a forged material for the face plate. The face plate of Anderson may be composed of several forged materials including steel, copper and titanium. The forged plate has a uniform thickness of between 0.090 and 0.130 inches.
Another invention directed toward forged materials in a club head is Su et al., U.S. Pat. No. 5,776,011 for a Golf Club Head. Su discloses a club head composed of three pieces with each piece composed of a forged material. The main objective of Su is to produce a club head with greater loft angle accuracy and reduce structural weaknesses. Finally, Aizawa, U.S. Pat. No. 5,346,216 for a Golf Club Head, discloses a face plate having a curved ball hitting surface.
The Rules of Golf, established and interpreted by the United States Golf Association (USGA) and The Royal and Ancient Golf Club of Saint Andrews, set forth certain requirements for a golf club head. The requirements for a golf club head are found in Rule 4 and Appendix II. A complete description of the Rules of Golf are available on the USGA web page at www.usga.org. Although the Rules of Golf do not expressly state specific parameters for a golf club face, Rule 4-1e prohibits the face from having the effect at impact of a spring with a golf ball. In 1998, the USGA adopted a test procedure pursuant to Rule 4-1e that measures club face COR. This USGA test procedure, as well as procedures like it, may be used to measure club face COR.
Although the prior art has disclosed many variations of face plates, the prior art has failed to provide a face plate with a high coefficient of restitution composed of a thin material, and the prior art has failed to disclose varying the face thickness based on the loft angle of the wood golf club head.
The present invention provides a set of wood golf club heads that vary in the thickness of the striking plate depending on the loft angle of the wood. Each of the woods has a striking plate that is compliant for lessening the loss of energy during impact with a golf ball. It has been determined that golfers with a higher club head swing speed tend to utilize drivers that have lower loft angles, typically seven, eight and nine degrees loft angles. It has also been determined that golfers with lower club head swing speeds tend to utilize drivers that have higher loft angles, typically ten, eleven and twelve degrees loft angles. Therefore, the thickness of a central region of the striking plate is varied according to the loft angle in an attempt to provide all golfers with a driver that will maximize their distance according to their specific swing speed.
One aspect of the present invention is a set of wood golf club heads including a first group of drivers and second group of drivers. The first group of drivers includes drivers with a loft angle of ten degrees or greater. Each of the first group of drivers has a striking plate with a central region with a thickness in the range of 0.090 inch to 0.120 inch. The second group of drivers includes drivers with a loft angle of less than ten degrees. Each of the second group of drivers has a striking plate with a central region with a thickness greater than the thickness of the central region of the striking plate of each of the first group of drivers.
Another aspect of the present invention is a wood golf club head having a body with a crown, a sole and a striking plate. The striking plate has a central region with a thickness in the range of 0.080 inch to 0.130 inch, and the thickness of the central region is dependent on the loft angle with the thickness of the central region increasing as the loft angle decreases.
Yet another aspect of the present invention is a method for designing a wood golf club head. The method is varying the thickness of a central region of a striking plate according to the loft angle wherein a higher loft angle has a thinner central region.
Yet another aspect of the present invention is a method for designing a set of drivers with loft angles of seven, eight, nine, ten, eleven and twelve. The drivers have the same or substantially the same club head volume, striking plate surface area, shape and appearance. The method is varying the thickness of a central region of a striking plate according to the loft angle wherein the central region of the striking plate of each of the seven, eight and nine loft angle drivers is thicker than the central region of the striking plate of the ten, eleven and twelve loft angle drivers.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.